The present invention relates to a power-distributing two-way transmission gear and a method of assembling same German Patent (DE-PS) 25 18 115 (Aug. 31, 1978) shows a transmission gear of this kind, the power branches of which drive a large gear through a spur gear stage. In this transmission gear, however, assembly and disassembly is possible only when at least one gear including the associated pinion of one power branch is provided to be adjustable exteriorly. When assembling has been effected, it is further necessary to precisely adjust the gear and the pinion in order to satisfy the structurally pre-given conditions.